Fine needle aspiration (FNA) is a widely used screening diagnostic procedure. Cells and tissues collected through FNA are used to make smears for quick staining and microscopic examination at the bed side and in most cases the collected cells and tissues are used to make a cell block for further studies. The current process of FNA is divided into two steps and using two separated systems respectively: The first step is sample collection and the second step is cell block preparation.
A syringe, combined with a fine needle, is conventionally most widely used as an aspiration tool in current clinical practice for sample collection.
A fine needle is briefly divided into three parts, the hub, the shaft, and the bevel. The hub is at one end of the needle and is the part that attaches to the syringe. The shaft is the long slender stem of the needle that is beveled at one end to form a point. The hollow bore of the needle shaft is known as the lumen. Disposable needles should always be used when preparing admixtures as they are presterilized and individually wrapped to maintain sterility. Needle size is designated by length and gauge. The length of a needle is measured in inches from the juncture of the hub and the shaft to the tip of the point. Needle lengths range from ⅜ inch to 3½ inches; some special use needles are even longer. The gauge of a needle, used to designate the size of the lumen, ranges from 27 (the finest) to 13 (the largest).
The fine needles used in conventionally FNA procedures have a small hub with a small space since the main function of the hub is to connect the shaft of needle to the syringe that provide a space for the storage of collected cells and tissues. The diameter of the conventional hub is less than 4 mm. During routine FNA procedure using a conventional needle and syringe, frequently, portion of the collected cells and small fragments of tissues stay in the small space of hub between the shaft of the needle and the nipple of the syringe. For majority of the FNA procedures, the stayed portion of the collected cells and tissues appears to be critical for the further studies and efficiently utilization of this portion of specimen remains as a problem. The current attempt to address this problem is to wash the syringe and the needle with a fixative (Formalin or ethanol) to remove all stayed specimen into the fixative in a container, and than separated the specimen material from the liquid fixative using centrifugation technique. After the centrifugation, supernatant (the fixative) is moved out; a matrix (“HistoGel”, argrose gel or others) is added and mixed with the cell or tissue pellet to make a gel-sample mixture. The tubular container contains the mixture is put in low temperature (40 C) for miniatures to make the mixture relatively solidified and than is moved out from the container, wrapped by a tissue paper and put into a tissue cassette for further treatment. Since only a small and finite amount of material can be obtained by FNA and the current process does not maximally use this limited amount of material. The limited amount of material collected through this procedure largely inhibits further classification of the disease, which results in more invasive procedures for a more conclusive diagnosis. This not only results in increased costs, but significantly delays the diagnosis as well.
The need remains for systems and methods which maximize the use of this limited material for different (H&E staining, immunocytochemistry and other) studies to permit a more conclusive diagnosis to be made by a single FNA procedure alone and without the need for more invasive procedures.